A process in which information is embedded in material for the purpose of identifying the material is referred to as watermarking.
Code words are applied to versions of material items for the purpose of identifying the version of the material item or for conveying data represented by the code words. Watermarking can provide, therefore, a facility for identifying a recipient of a particular version of the material. As such, if the material is copied or used in a way, which is inconsistent with the wishes of the distributor of the material, the distributor can identify the material version from the code word and take appropriate action.
In co-pending European patent application 1 324 263 A, there is disclosed a watermarking system comprising an encoding data processor operable to generate at least one marked version of an original item of material by introducing one of a predetermined set of code words into a copy of the original material item. The apparatus comprises a code word generator operable to generate the code word having a plurality of code word coefficients, and an encoding processor operable to combine the code word coefficients with the material item. Each of the plurality of code words of the set is uniquely associated with a data word having first and second fields. Each of a set of values of the first field is represented as a first part of the code word having a first plurality of coefficients, and the second field is represented as a second part of the code word having a second plurality of coefficients.
The first and second fields can be assigned to different associated parameters such as for example address parameters. The first field could therefore identify the country of distribution of the material, whereas the second field could identify a particular distribution outlet within the country. A watermarking system can be formed for identifying a point of distribution of pirate copies of video material.